In general, absorbent articles such as a sanitary napkin, an incontinent pad, a breastfeeding pad, and the like, are known to include a liquid permeable top layer, a liquid impermeable back layer, and a liquid retentive absorbent core disposed between the top layer and the back layer. Such an absorbent article is required to cause body fluid, such as blood, urine, and the like, to rapidly migrate to the absorbent core where it is absorbed and retained with no leakage.
As an absorbent article for absorbing/retaining body fluid without permitting leakage, there is known one as disclosed in Japanese Laid-Open Patent Publication No. 61 (1986)-56647; another as disclosed in Japanese Laid-Open Patent Publication No. 58 (1983)-36552; and still another as disclosed in Japanese Laid-Open Patent Publication No. 59 (1984)-166146.
In the absorbent article disclosed in Japanese Laid-Open Patent Publication No. 61 (1986)-56647, a top layer, a back layer, and an absorbent member are folded integrally, and overlaid at a widthwise central portion of the absorbent article.
In the absorbent article disclosed in Japanese Laid-Open Patent Publication No. 58 (1983)-36552, the absorbent member is an overlaid structure having two layers consisting of an upper layer and a lower layer, with a liquid impermeable barrier disposed therebetween.
In the absorbent article disclosed in Japanese Laid-Open Patent Publication No. 59 (1984)-166146, the absorbent member contains a fusible thermoplastic resin, this absorbent member being folded and overlaid at its widthwise central portion, and the absorbent member is partially, thermally bonded so that its folded form is retained.
Any one of these absorbent articles is designed such that, by forming the widthwise central portion thick in dimension, the widthwise central portion is reliably contacted with the body fluid leaking portion and a widthwise positional displacement is prevented, thereby avoiding a possible leakage of body fluid.
However, in the absorbent article disclosed in Japanese Laid-Open Patent Publication No. 61 (1986)-56647, since the back layer is disposed at the widthwise central portion between one absorbent member and another absorbent member and migration of the body fluid is interrupted by this back layer, a sufficient body fluid absorptive ability is not exhibited. Thus, there is the possibility that leakage of body fluid may occur.
Also, in the absorbent article as disclosed in Japanese Laid-Open Patent Publication No. 58 (1983)-36552, migration of the body fluid is interrupted by the liquid impermeable barrier at the widthwise central portion and a sufficient body fluid absorptive ability is not exhibited. Therefore, there is the possibility that leakage of body fluid may occur.
In the absorbent article disclosed in Japanese Laid Open Publication No. 59 (1984)-166146, since migration of the body fluid is interrupted by the melting thermoplastic resin contained in the absorbent member and a sufficient body fluid absorptive capacity is reduced, a sufficient body fluid absorptive ability is not exhibited. Thus, there is the possibility that leakage of body fluid may occur.
Further, as an absorbent article capable of absorbing/retaining a body fluid with no leakage, there has heretofore been known an absorbent article which employs a liquid-shrinkable member which tends to shrink elastically by absorbing a body fluid. Such an absorbent article has the advantage that it can easily be manufactured in the state that the liquid-shrinkable member has no elasticity.
An absorbent article employing a liquid-shrinkable material is that in which a plurality of liquid-shrinkable members are disposed in parallel relation to each other in the longitudinal direction of the absorbent article, generally over the entire central portion at the inside of the absorbent member in a thickness-wise direction. Thus, when a body fluid invades, the absorbent member is subjected to a shrinking treatment due to the shrinkage of the liquid-shrinkable members. Another absorbent article is that in which the liquid-shrinkable members are disposed outwardly of each side of the absorbent member in such a way as to cross the longitudinal direction of the absorbent article, so that when the body fluid invades, an external part of each opposing side of the absorbent member stands up due to the shrinkage of the liquid-shrinkable member. A third is that in which a liquid-shrinkable member is disposed on an external part of each opposing side of an absorbent member along the absorbent article, in a longitudinal direction thereof, so that when a body fluid invades, the absorbent article has a bent shape in the longitudinal direction due to the shrinkage of the liquid shrinkable member.
However, an absorbent article in which the absorbent member is subjected to a shrinking treatment has shortcomings in that since the liquid-shrinkable member is present generally over the entire central portion at the inside of the absorbing body in the thickness-wise direction thereof and since the absorbent article as a whole is provided with small irregularities, leakage tends to occur due to the motion of the wearer. With respect to the absorbent article in which the external part of each opposing side of the absorbent member stands up, they have shortcomings in that since the external part of each opposing side which stands up does not have a body fluid absorbing ability, leakage is likely to occur beyond the external part of each opposing side, due to the motion of the wearer. Also, with respect to the absorbent article which is bent in the longitudinal direction, since the liquid-shrinkable member is disposed at an external part of each opposing side of the absorbent body, the absorbent body does not shrink integrally with the liquid-shrinkable member, resulting in unfavorable possibilities wherein the absorbent article is not effectively bent, the fitness is degraded, and among all, the problem of liquid leakage, which is most likely to occur at the side edge of the absorbent article is not obviated. In addition, since no improvement is seen in absorptive capacity of a body fluid in any of the above conventional absorbent articles, they cannot appropriately cope with a large quantity of body fluid, thus inevitably resulting in leakage.
It is, therefore, the object of the present invention to provide an absorbent article which is excellent in body fluid absorptive capacity and fits nicely to the wearer's body, and which is capable of preventing the possible leakage of body fluid, irrespective of the quantity of body fluid and movement of the wearer.